Converter system for electric railways



2 Sheets-Sheet 1.

(No Model.)

0. s. BRADLEY. CONVERTER SYSTEM FOB. ELEGTRIGRAILWAYS No. 508,807.

Patented Nov.. 14, 1893.

me NATIONAL Luxeon/Puma COMPANY.

wAsnxNGYou. o. c.

2 Sheets-Sheet 2i (No Model.)

- p8. 8. BRADLEY. CONVERTER SYSTEM FOR ELECTRIC RAILWAYS.` 180.808,80?.

Patented Nov. 14,1898.

. o UNITED STATES PATENT CEEICE.-

' oHARLEss. BRADLEY, oE YoNKERs, ANEW YORK.

CONVERTER SYSTEM FOR ELECTRIC RAILWAYS'.

SPECIFICATION forming part of Letters Patent No. 508,807,V dated November 14, 1893. Applieationled May 31, 1887. Serial No. 239,786. (No model.)

T all whom t may concern:

Be it known that I, CHARLES S. BRADLEY, of Yonkers, lVestchester county, New York, have invented a new and useful Improvement in Electric Railways, of which the following is a specification. Y

The object of this invention, which is especially applicable and important in ordinary street or surface railways, though applicable to electric railways ot` all kinds, is to enable the ordinary rails of the track on which the car travels to supply the current for driving the cars,4 by feeding the rails with a current of such low electro-motive force that the dan ger of shock to animals, and the loss by leakage in wet weather or otherwise is avoided; andaccidental short-circuiting between the rails becomes a matter of less importance;

. and to accomplish this witho ut involving very large copper or other conductors to convey the necessary electrical energy from the sta tion where it is generated to the moving cars.

By my invention I am enabled to make use of lthe rails of ordinary horse-car or other street roads now in use to supply the driving current to the cars without the necessity of tearing them up or changing them in any rnaterial way. To accomplish this I have devised a system in which the cars or vehicles running on the track take their supply of cur# rentdirectly from the ordinary track rails in the form of a current of very low electrofmotive force, and the electrical energy is conveyed from the generatin'gistation or source of supply in the form of-a current of comparatively high electro-motive force and converted at points along the track into the low electro-motive force current which is fed to the rails. The low electro-motive force current 'taken up from the rails bythe moving cars or vehicles is then used either directly to drive' the car,ror is reconvertedinto acurrent bf comparatively high electro-motive `force, which is used to drive the car.

I will describe my invention by reference to A the accompanying drawings, in which- Figure l is a plan View of a track, showing the conductors and apparatus for supplying the rails with the current-,according to my invention. Fig. 2 is a detail view of the same, showing an improved form of'converter which -ply of electric current.

I have devised to convert the high electro-mo tive force current into 'a low electro-motive force current. Fig. 3 is a view in sectionv of the converter on the plane 3, 3. Fig. lis another form oi' converter; and Fig. 5 isa plan View of the track andthe driving machinery of the car, constructed according to my invention. v

A and B represent the rails of a track, which may be any kind of trackthe ordinary iron or steel rails of a horse-car or other railroad, for example. Alongside or between the rails of the track I lay current-conveying conductors, C D,which extend to and are connected with the generating station or source of sup- These conductors maybe arranged overhead or alongside of the track, but preferably underground alongside of or between the track rails, or under the pavement in a proper conduit. They are' fed with a current of high electro-motive force from a suitable dynamo-machine or source of supply 'at the generating station. I have shown them connected with 'an alternating current dynamo machine, so that they are fed with an alternating current of high electro-motive,*forcer-say a thousand or several thousand volts. These conductors may be Vmade 'of copper or of any other material of the necessary conductivity, and need only be large enough to 'carry the required amount of electrical energy of the given volts to operate the cars without -too much loss of current due to resistance, and-without overheating; 'the' necessary size depending of course upon the' electro-motive force of the current used, and the amount of power re quired to operate all the cars at any one time. 'lhe higher the electro-motive force of the current used the smaller can these conductors be made, both on account of the less amp res they Awill be required to carry to supply a'given power, and on account ot' the less loss of current in them due `to resistance. By using a lcurrent of quite high electro-motive force,-say over a thousand volts-I ain enabled to convey the required amount of elecf trical energy -to operate the number of cars in the form of a currentof so few/ampres, that only a very small copper conductor, or a mere wire, will be required. V'For example, it there IOO are-say ten cars to be supplied from the same set of conductors requiring live horsepower each, with an efficiency of sixty per cent., and an electro-motive force of twelve hundred volts to be used, the capacity of the conductors need only be sufficient to carry fifty ampres in order to furnish the required fifty horse-power. At points along the track I arrange converters F F, or transforming apparatus, which are connected with and fed from the conductors C D, and may be placed at any desired points above or below the ground. The primary coils or circuits of these converters are connected, as stated, with the feeders C D, and their secondary coils or circuits are connected directly with the rails from which the cars take up the current. If Vthe ordinary rails ot' the trackbe used vfor this purpose, .the secondary coils of the converters are connected, one end with one rail, and the otherv end 1with the othery rail, as clearly shown. The connections with the rails may be made at a-nyfdesired points along the track, and as frequently as desired, depending upon various-conditions; but in order to avoidthe necessity of carrying anycurrent through the joints of the rails, I provide connections at every secondgjoiut of the rails, as shown, makingthe connection with the rails on each side of thej oint, so tha-tthe current passes both ways, and-the same connection feeds the rail for-the length of one rail either Way, as clearly shown.

The ordinary track rails being thirty feet` lon-g, this would `make the connections to the would be required to pass through the ordinary joints in the rails. provision would have to be made to connect the rails with each other, which Would be -verydifticul it' not impossible, with the use of suc-h extremely low electro-motive forces as can be used-in my system. If d esiredaseparate converter may be used at each point Where connection isV made to the track rails, as I have lshown in Fig. l; or several connections may be taken from the same converter.

The ,convert-ers or transforming apparatus F F are constructed so as to convert the high electrofmotive force current supplied to them by thefeeders-C D into currentsof extremely loweleetro-,motive force; and it is these very low'electro-motive force currents which are supplied-to the rails of the track, and taken up ,therefrom bythe moving cars. Aerl=y cons tructing the converters in the wellknown man-ner, the electro-motive force pf the .original current may be` reduced to any desired eXte,nt,-to .only a very few, sayiive volts for `less-.so that the electro-motive force between the two rails of the track is so low that no material loss results by leakage between the rails, even in wet weather, or from other causes,- short circuiting between the rails becomes amatter much less serious, and allldanger of shock to animals is avoided. If the rails themselves were used to convey the rails about sixty feet apart, and no current Otherwise a special the track railsA B, as shown.

current-from the generating station, the current would have to pass through the joints of the rails, and special connections would have to be made between the abutting ends of the rails forthis purpose, and the loss of electril cal energy resulting from the resistance of the joints and the rails themselves, provided vbe unobjectionable in streets and-other-localities; to avoid the necessityof passing the-current through the joints of the rails;l,and to convey the current from the generating station to the tracks in a way which-does not require large and expensive copper conductors, and with only a small `and permissible loss of electric energy.

In Fig.2, I have shown a more detailed view of the track rails and'connections, Aand a very simple and inexpensive form of con- Vverterwhich I have devised, applicabl-eto .thisI purpose. G is the primarycoilor conductor of the converter, which I make in the form of an oblon-g coil composed of `the proper number of turns tosuiit the electro-.motive force of theprimary currentwhich is .fed to itfrom the feeders C D. The two straight partsfof this coil are surrounded by copper or other met-al tubes H H, which are connected together at one endbya copper collar I, so that the tubes are electrically in series.` These two copper tubes in series form the secondary .conductor of the converter, and are connected at their ends by heavy copper conductors J J with suitable chairsor connecting devices which make proper-electrical connection with These copper tubes H I-I are lr'nade of a sufficient length to give the required electro-motive forcevfor the rail current, and-of a suficient cross-section to carry the required number of ampres. Surrounding the copper tubes orv envelopes are shells or tubesof iron K'K for concentrating the lines of force, which should of course be laminated at right angles to the length of the tube, and may conveniently be formed of iron wire wrapped around the tubes, as shown, and having its convolutions insulated from one another. change of the current in the primary coil G induces an alternating current in the tube or secondary conductor H I-I, the electro-motive force of which is extremely low compared with that of the kprimary circuit;` the amount of reduction being determined, as is Wellknown, by the'relative lengths of the primary and secondary conductors `acting 'upon each other in the converter. The converters may The alternation or' IOC IIO

well be inclosed in water-tight cast iron boxes as I have shown, so that they can be placed under ground.

conductors consist of two coils of relatively coarse and fine wire, H and'G, -wound vupon the same laminated iron ring. r

Fig. 5 shows the' apparatus upon the car,

which I have devisedfor taking up the low tension current from the track rails and ap-l plying it to the work of propelling the car.:

The current may be taken up from the track in various ways. Ihave shown for this purpose brushes L L which are mounted upon the overaconsiderable area, and in snowy or wet weather they may be preceded by Scrapers or sweeping devices which clean' the surfaces of the tracks, or the necessary connections with the rails may be obtained by means of specialvrollersor by the wheelsvof the car itself, Whichlatter plan of taking up the current I have also represented, the tires of Vthe driving wheels on the'car axle being insulatedfrom one anotherand the current being taken from the wheels by suitable brushes bearing thereon,a nd mounted upon the car, as I vhave indicated by dotted lines. The current taken up from the trackrails may then be conveyed either through an electric motor of a'proper construction to be operated bysuch a low volt circuit current, or it may be passed through the primary circuit M of a converter carried bythe car itself, and there reconverted into a current of higher electro-motive force, whatever it is desired to operate the ,motor with, as I have shown in the drawings. To accomplish this and to enable the speed or power of the motor to be easily and efficiently controlled, I

`construct the converter so that its secondary coil or circuit is divided uppinto a number of sections,which are respectivelyconnectedwith the points of aswitch P, and which may be ar-f rangedin series, as shown, so that the turning of theswitch throws more orless of the sections into the motorcircuitin series, therebyvaryin g the electro-motive'force of the current supv as I have shown.

` be desirable to employ a continuous current motor, and feed itby rectifying the alternating current obtained from the secondary of the converter. To accomplishthis, any suitable means forV rectifying the current may be employed. I have shown for this purpose a rectifying switch or commutator R, operated by a little constantspeed alternating-current motor S, which is fed from an independent r`secondary coil on the converter, :as shown.

This little motor which requiresonly power enoughto turn the commutator R, is provided with apermanet-magnet field, and'being operated byan alternating current Will only run, as is well-known, at a certain speed, and will preserve exactly that speed. n By making the sections of the commutator R of theproper number and in the proper positions to agree with the reversals of the secondary current, the commutator4 R will work inp'unison withl the alternations of ,the current and operate ,to reverse the connections with the` motor synchronously with the reversals ot' the secondary current, so that the current always passes through the motor Q inthe same direction. The motor Q7 being mechanically connected by a sprocket belt, for exam ple, orin any other satisfactory way with thev driving wheels, the motive power for` propelling the car is thus supplied. p I Y In my system of conveying the electrical energy from the generating station o r source of supply to the vmoving cars or vehicles, a continuous or intermittent or any other form ofelectric current or ,energy may be employed instead of the alternating current to convey`- IOO the power from the generating station to the point or points where itis converted intoV a current of different electro-motive forcehvvhich'v is'sup'plied to the rails or conductorsl from which the traveling vehicles take their current; and the conversion of the electric current from a current ofyhigh electro-motive Vforce into a current of lowv electro-'motive force can be effected by various forms of converters or transforming apparatus and in various ways. It may be preferable Vunder some conditions to employ a continuous current to convey the electrical energy from the generating station to the converters,andthe conversion may be eiected among other ways by varying the current or producingintermittent changes kin it. Y,

.My invention is also applicable toA cases where the moving cars or vehicles,inst ead ofl taking their supply ofV current from the track.

IIO

rails, take their supply of, current from over l l head or other conductors or vrails extendingy parallel with the track. in which cases sucht.

overhead or extra conductors would be supplied from the converters in the same way as I have shown the ordinary trackrrails, supplied.l For example my invention may be applied to electric railways in which the `cars take. their supply'of current fromoverhead suspended naked wires or conductors. These vwires or conductors beingvcexposed Vor in danger of having something come in electrical contact with them, can be supplied with the comparatively low tension current by the converters, according to my invention.

What I claim as my invention, and desire to secure by Letters Patent, is-

l. The combination of a generating station or source of supply of electric energy, electric feeding conductors supplied thereby and eX- tending along the line of a railway, track rails formed of jointed sections or lengths in the usual way, cars adapted to travel thereon and provided with electric propelling apparatus and means for taking the supply of currentl from the track rails, and electric connections atY every second joint of the rails on each side of the joint for supplying the current furuished by the feeding conductors to the rails atthese points, thereby avoiding the necessity of passing the current through the ordinary rail joints.

2. In an electric railway system, the combination of a stationary source of electricity, a track or roadway insulated feeding conductors extending along the latter and supplied i rom said Source with an alternating or intermittent current of high electro-motive force, secondary or Working conductors also extending along the roadway, electrical transforming devices arranged at Aintervals along the roadway and having their primaries in circuit with said feeding conductors and their secondaries connected to said working conductors, an electric motor on a vehicl'eand a second 'transformer carried by said vehicle and havductors extending along the latter and supplied from said source with an alternating or intermittent current of high. electro-motive force, secondary or working conductors also extending along the roadway, electrical transforming devices arranged at intervals along the roadway and having their primaries in circuit with said feeding conductors and their seconda-ries connected to said working conductors, an electric motor ofn a vehicle, and a second transformer carried by said vehicle and having its primary and secondaryin circuit respectively with the working conductors and the said motor and having a switch for varying the resistance of the secondary of said transformer, substantially as set forth.

CHARLES S. BRADLEY. Witnesses:

CHARLES G. CURTIS CHAs. J. MAGUIRE. 

